Influence of Micro-texture Distribution and Straining Direction on the Ridging of Ferritic Stainless Steels

Abstract

Ridging means the appearance of surface profile undulations, i.e. peaks and valleys, as a result of plastic strain. The reasons for the different ridging behaviour of industrially produced, stabilized ferritic stainless steel sheets (EN 1.4509) have been investigated after straining in the rolling and transverse directions with low and high resistance towards ridging. The evolution of macro-texture has been measured by X-ray diffraction (XRD) both before and after ridging tests in the rolling and transverse directions. The macro texture results showed that straining along the rolling direction strengthened the α fibre whereas the γ fibre was strengthened by grain rotations after straining along transverse direction. Electron backscatter diffraction (EBSD) imaging was used to establish the micro-textural variations over the thickness of the sheets among the high and low ridging materials. Mean orientations of individual grains determined from the EBSD data were utilized to calculate plastic strain ratio r-values by considering all slip systems weighted according to their Schmid factors. The calculated r-values were used to predict the ridging surface profile after straining along the rolling and transverse directions. The results demonstrated the influence of local variations in micro-texture on the severity of ridging.

A Combined Microscopy Study of the Microstructural Evolution of Ferritic Stainless Steel upon Deep Drawing: The Role of Alloy Composition

“…Several studies have investigated the texture evolution of FSSs during forming processes using different techniques such as X-ray diffraction (XRD) [8][9][10][11][12], electron backscatter diffraction (EBSD), and scanning electron microscopy (SEM), [8][9][10][11][12][13][14][15][16][17][18] and only a small number of studies employed transmission electron microscopy (TEM) [13,19]. Some of these studies focused on cold-worked FSSs.…”

“…Others studied the texture evolution to understand the ridging process that FSSs may experience during forming, like Ma et al [16], who found that this defect is avoided by preventing the formation of coarse bands and grains with the {001} component in 430 and 430 LR. However, most of these studies focused on the most popular standard grade of FSSs, AISI 430 [11,16], while others explored the texture evolution of modified grades with higher contents of Ti and Nb, which have improved corrosion resistance and weldability [8][9][10][13][14][15][17][18][19]. None of these works studied the influence of the slight modification of the typical alloy elements of AISI 430 standard composition, such as Si, Mn, Cr, C, and N. Moreover, there is a lack of comprehensive and comparative analysis of the texture evolution of different grades of FSSs after deep drawing and its relation to their formability and mechanical performance.…”

In-situ EBSD study of 409 L ferritic stainless steel during tensile testing

“…It is generally believed that coarse banded structure of colonies [5], known as grain colonies, is responsible for ridging. Different grain colonies and matrix are likely to show different plastic anisotropies [4][5][6], leading to ridging. In almost every process of FSS manufacturing, such as casting [5,7,8], hot rolling [9,10] and cold rolling [4,8], the correlation between grain colonies and ridging has been observed.…”